1. Field of the Invention
The present invention relates to a disk drive device for rotating and driving a recording disk.
2. Description of the Related Art
A hard disk drive is widely available as a storage medium used for a storage device or like of a computer. The rotation precision of the hard disk drive has markedly improved and, accordingly, there is a growing demand for higher density and larger capacity in the hard disk drive. For example, such a highly advanced hard disk drive is disclosed in Japanese Patent Application Publication No. 2007-198555 featuring a motor equipped with a fluid dynamic bearing.
In a hard disk drive, a disk with recording tracks formed thereon is rotated by a brushless motor at high speed. To read/write the magnetic data contained in the recording tracks, a read/write head is arranged over a recording disk with a very small clearance between the read/write head and the surface of the recording disk.
As a way of promoting the higher capacity of the hard disk drive, a method is available where the width of the recording tracks is reduced and the position of the read/write head relative to the surface of the recording disk is further reduced. However, this arrangement has the following drawbacks. That is, a vibration due to the torque ripple of the brushless motor and the resonance in a secondary rocking mode may become larger. And the reduction in the width of the recording tracks may cause a vibration, which in turn vibrates the read/write head. Thus the trace of the recording track may be disturbed.
Also, further reduction of the clearance between the record/write head and the recording disk results in a large variation in the clearance even with a small amount of vibration in the read/write head. Thus, whenever the trace of the recording track is disturbed and the amplitude of an output signal of the read/write head varies, the frequency at which the malfunction occurs, at the time the data in the hard disk drive is read and written, may increase.